Typically an audio or media player will contain a wide range of various audio and video tracks or files. These tracks can be collected from various sources such as being purchased or downloaded from websites, ripped from CD's or audio tracks, or shared from friends. Due to the diverse nature of sourcing tracks and the unknown recording and content conditions the user is likely to experience a wide range or disparity in the perceived volume or loudness level during playback of various audio tracks. This wide range of loudness levels can be unpleasant for the user as they have to manually adjust the volume for each track. Furthermore in some circumstances the wide range of loudness can cause a psycho-acoustical shock where the volume level increase is significant to cause temporary shock to the user.
Since audio files on such audio and media players are typically stored in a compressed format the audio player is unlikely to attempt to normalise the signal level before playback or insertion into a playlist or queue due to the processing required unless specific measures are taken such as provision of additional metadata about the volume or loudness information.